/Engine/Plugins/Experimental/ScreenReader/Source/ScreenReader/Public/GenericPlatform/ScreenReaderBase.h
Unregisters a provided user Id from the screen reader framework and deactivates the user. The unregistered user will no longer receive or respond to accessible events and input. Nothing will happen if the provided user Id has not been registered with the screen reader.
Returns true if the provided user Id has been successfully unregistered. Else returns false.
bool UnregisterUser ( int32 InUserId )